In a GSM/EDGE network, in order to transmit RLC, Radio Link Control, data blocks between two nodes such as, e.g. a Base Station Controller, a BSC, and a Mobile Station, an MS, a so called Temporary Block Flow is used. Use may be made of an existing TBF between the two nodes, or, in the absence of an existing TBF, a TBF is established between the two nodes. A TBF is used in one direction only, so that in order to transmit RLC data blocks both in the uplink (MS to BSC) and downlink (BSC to MS) directions, two TBFs are needed, one downlink TBF and one uplink TBF. An RLC data block which is sent in one direction is replied to by means of an ACK/NACK message in the other direction, via a TBF arranged for transmission in that other direction.
In order to establish a TBF, a number of control messages are exchanged between the MS and the BSC. Similarly, when releasing a TBF, control messages are transmitted between the BSC and the MS. Thus, if there is active exchange of data between an MS and the BSC in both directions, i.e. downlink (DL) and uplink (UL), and this exchange of data then ceases, a large number of control messages will have to be sent in both directions, both in the UL and the DL directions, in order to release the DL TBF and the UL TBF. Naturally, it is a desire to minimize traffic on the channels on which control messages are transmitted.